I don't mind having a dumb and straightforward heroine. I mean she's not typical shojo-kawaii-dumb-no-spine-crybaby and she's not foresign-ish "faceslapping" "genius" as we often see in CN isekai.
I think she's fine and refreshing.
As for leaving for good - she's attracted to ML right now and angered by her rival. It's hard to make wise decisions in such situation. I suppose you may belive in fighting for love in her age.
Don't forget that she's living her life now. She's not reincarnator nor she came back in time after gaining painful experience. She just read something in book. So her whole image is logical and consistent.
I think she's fine and refreshing.
As for leaving for good - she's attracted to ML right now and angered by her rival. It's hard to make wise decisions in such situation. I suppose you may belive in fighting for love in her age.
Don't forget that she's living her life now. She's not reincarnator nor she came back in time after gaining painful experience. She just read something in book. So her whole image is logical and consistent.